[Insight-developers] RecursiveMultiResolutionPyramidImageFilter -- questions about fixing bug 8482

[Tom Vercauteren]

Hi Kent,

> In making RecursiveMultiResolutionPyramidFilter consisitent with
> MultiResolutionPyramidFilter, I made the smoother use ImageSpacing.  This is
> consistent; is it desirable?

Both multi-resolution pyramids define their sigmas in terms of pixel
sizes, not physical space. Therefore, they should use a smoother with
UseImageSpacingOff. This is what
http://public.kitware.com/Bug/view.php?id=503 says.

I really don't understand why ITK 3.12 introduced UseImageSpacingOn
instead of UseImageSpacingOff in the smoother of
MultiResolutionPyramidFilter. This makes no sense to me and broke
bachwards compatibility.

A patch should really not introduce this bug also in
RecursiveMultiResolutionPyramidFilter. I would definitely vote for
patching MultiResolutionPyramidFilter w.r.t. smoother spacing. This
will make both pyramids a little more consistent and would fix the bug
introduced in 3.12. It would not be strictly backwards compatible with
3.12 but should be with 3.10 and earlier.

Let me know if I am missing something.

Regards,
Tom